The present invention relates to apparatus for introducing photosensitive material into and for removing photosensitive material from containers, particularly for unloading and loading cassettes for X-ray film. Still more particularly, the invention relates to improvements in apparatus wherein a container or cassette which contains a sheet or plate of exposed film is relieved of its contents and is thereupon recharged with a sheet or plate of unexposed film.
German Pat. No. 1,497,446 discloses an apparatus wherein a cassette which contains exposed X-ray film is inserted into a lighttight housing and is placed onto a tiltable table while the table is held in horizontal position. The table is thereupon tilted to one side, the cassette thereon is unlocked by a first unlocking device, and the film is allowed to leave its interior by gravity. The cassette is thereupon locked and the table is tilted in the opposite direction to a station where it is unlocked by a second unlocking device so that it can receive a sheet of unexposed film. In the next step, the table is tilted back to the horizontal position and the loaded and locked cassette is removed from the housing.
A drawback of the patented apparatus is that the removal of an exposed film and the insertion of an unexposed film take up a relatively long interval of time. Furthermore, the apparatus is complex because it must be equipped with two discrete unlocking mechanisms. Still further, the extent to which the cassette is opened is rather small so that a sheet of film therein is likely to be held against evacuation by gravity while the cassette is located at the evacuating station. The insertion of a fresh sheet at the loading station also presents problems. As a rule, such cassettes contain layers of foamed material which expands when the cassette is caused or allowed to open. Unless the angle between the pivotally connected sections of the cassette is very large (when the cassette is held in open position), the layer or layers of expansible foamed material will interfere with gravitational descent of an exposed sheet and/or with introduction of an unexposed sheet. It is desirable to evacuate exposed sheets by gravity because this simplifies the construction of the apparatus; on the other hand, the aforementioned layer or layers of foamed material often prevent gravitational descent of sheets from a slightly open cassette so that the exposed sheet is likely to be transported beyond the unloading station.
In a cassette which is used in a machine for making mammograms, the sheet of unexposed X-ray film must be inserted all the way into the interior of the cassette so that the front edge portion of the sheet can be placed as close to the chest of a patient as possible. This enables the X-ray machine to make images of entire breasts. Reference may be had to commonly owned copending application Ser. No. 832,884, filed Sept. 13, 1977, now U.S. Pat. No. 4,152,593, by Manfred Schmidt et al. This application discloses an imaging chamber wherein one edge of the film is located in immediate proximity of that portion of the chamber which is nearest to the body of the patient during radiographic examination of her breasts.